705.Design HashSet

tags: Easy,Design,Array,Hash Table,Linked List

705. Design HashSet

題目描述

Design a HashSet without using any built-in hash table libraries.

Implement MyHashSet class:

• void add(key) Inserts the value key into the HashSet.
• bool contains(key) Returns whether the value key exists in the HashSet or not.
• void remove(key) Removes the value key in the HashSet. If key does not exist in the HashSet, do nothing.

範例

Example 1:

Input
["MyHashSet", "add", "add", "contains", "contains", "add", "contains", "remove", "contains"]
[[], [1], [2], [1], [3], [2], [2], [2], [2]]
Output
[null, null, null, true, false, null, true, null, false]

Explanation
MyHashSet myHashSet = new MyHashSet();
myHashSet.add(1);      // set = [1]
myHashSet.add(2);      // set = [1, 2]
myHashSet.contains(1); // return True
myHashSet.contains(3); // return False, (not found)
myHashSet.add(2);      // set = [1, 2]
myHashSet.contains(2); // return True
myHashSet.remove(2);   // set = [1]
myHashSet.contains(2); // return False, (already removed)

Constraints:

• 0 <= key <= 10⁶
• At most 10⁴ calls will be made to add, remove, and contains.

解答

C#

public class MyHashSet {
    const int Size = 1 << 10;
    const int Mask = Size - 1; 
    List<int>[] set = new List<int>[Size];

    public MyHashSet() { }
    
    private List<int> this[int key]
        => set[key & Mask] ??= new List<int>();

    public void Add(int key) {
        var slot = this[key];
        if (!slot.Contains(key)) {
            slot.Add(key);
        }
    }
    
    public void Remove(int key) {
        var slot = this[key];
        if (slot.Contains(key)) {
            slot.Remove(key);
        }
    }
    
    public bool Contains(int key) 
        => this[key].Contains(key);
}

JimMay 30, 2023

Python

class MyHashSet:

    def __init__(self):
        self.hashset = set()
        
    def add(self, key: int) -> None:
        self.hashset.add(key)

    def remove(self, key: int) -> None:
        if self.contains(key):
            self.hashset.remove(key)
        
    def contains(self, key: int) -> bool:
        return key in self.hashset
        

Ron ChenTue, May 30, 2023

Reference

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